LB7: Pistons ?
- Thread starter TrentNell
- Start date
nathan was it 5-30 or 5-40??
I run 15-40 and my oil pressure is still only like 23-ish psi hot at idle.
this is an LBZ shortblock/oil pump
my original LLY had the same oil press as my current LBZ shortblock
my built motor had a little better; maybe 28-29 hot at idle. Then it broke one of those POS rods and had 0 psi oil pressure.
ben
I run 15-40 and my oil pressure is still only like 23-ish psi hot at idle.
this is an LBZ shortblock/oil pump
my original LLY had the same oil press as my current LBZ shortblock
my built motor had a little better; maybe 28-29 hot at idle. Then it broke one of those POS rods and had 0 psi oil pressure.
ben
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That is most definitely a modified piston. Looks like it might be delipped, but it's hard to tell without seeing better pics of the bowl. At the very least, it has had valve reliefs cut into it. Not sure if it is coated or not. What I can say it is without a doubt is an LBZ piston, not an LB7 piston.I don't know hardly anything when it comes to pistons.... My buddy gave me one and said it came out of a very fast duramax that likes a ridiculous amount of nitrous
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nathan was it 5-30 or 5-40??
I run 15-40 and my oil pressure is still only like 23-ish psi hot at idle.
this is an LBZ shortblock/oil pump
my original LLY had the same oil press as my current LBZ shortblock
my built motor had a little better; maybe 28-29 hot at idle. Then it broke one of those POS rods and had 0 psi oil pressure.
ben
Yes, I blew a hole in a stock LBZ piston. Yes, I ran my truck hard before I put the twins on. And yes, I saw my oil pressure dropping to below 30 psi while going down the highway running 5w-40 synthetic motor oil.
When I blew a hole in the piston I had about 10,000 miles (total approx. 48k miles) and probably well over 50 1/4 mile passes since installing the twins. If I had hurt the pistons prior to installing the twins, I think I would have had a problem before I did.
The day right before I blew a hole in my piston, I towed a very small camper (16' aero lite) back from Yellowstone. I had 5 people in the truck and a bed full of luggage and assorted camping stuff. I didn't weigh the truck, but I would estimate it to be somewhere around 14k lbs gross. I was running a small tune (probably mid to low 500 hp). While on the trip back, I watched my oil pressure drop to below 30 psi with my RPMs at more than 2,000. I know this because my TTS lift pumps shut off if oil pressure drops below 30 psi, and they were shutting off while I was going up hills. I don't know how low it got because my oil gauge never really went below 30. On my trip back, I was towing through mountains and stuff, and I was watching my pyro very closely. I never let my EGTs go over 1000 °F on the whole trip back. The next day, with the smaller tune still in my truck, I had to go drop my brother in law off at the airport, and on my way home, I got on it while getting on the interstate. That's when it happened. I don't think it's a coincidence. I believe the oil cooling is a big part of why my piston blew. That's why I bought an oil temp gauge to put in my truck. I want to see how hot my oil is after it leaves the cooler. I would like to add that my piston didn't really crack. It had a hole blown in it. Looked like someone took a blow torch to it.
Sorry man wasnt trying to bring your truck into this , good info to though . def sounds like oil had a factor in your failure . i have thought about an upgraded oil cooler and a temp gage . i have seen a lbz crack a piston on just a bully dog tuner .
, good info to though . def sounds like oil had a factor in your failure . i have thought about an upgraded oil cooler and a temp gage . i have seen a lbz crack a piston on just a bully dog tuner .
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I don't mind sharing about my failure. I would have posted my experience earlier, but since you were talking about LB7 pistons, I thought it was kind of irrelevant. LB7 and LBZ pistons aren't even in the same league, IMO.
ya what brought them into it was the fact that they are having better luck surviving in trucks with twins at big power . and wondering if the cooler egt's are the ticket , and if that was true then by all rights with the lb7 piston being superior in streingth that one might live at high horse power in stock form ( rods being replaced of course ) say to 750 hp if they were kept cool in the process .
Maybe it is engine oil temperature more than egts. Are egt's fine if the cool oil keeps cooling the piston then when the oil gets hot and provides insufficient cooling then egt's play a factor? Fact: Pistons and cylinders are heat generators. Egts are only one source of measuring heat. Engine oil temperature gives the egts a degree or a severeity level. So if you keep egt's in check, then engine oil temps stay in check. Do briefly and extremely high egt's make little difference when oil temps stay cool? Egt's over time do the damage. I think egt's are only severe if given time, kind of like the difference between a 3rd degree burn and a 1st degree burn. Both do their damage. If you get enough third degree events then will you eventually end up with 1st deg consequence?
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I don't have any data. I got my gauge about a week before I parked the truck for the teardown, and I never got a chance to install it.
I disagree. I decided I was going to put it after the cooler because I wanted to see the temperature of the oil going to the bearings and pistons. If the heat is causing an oil pressure drop, it will show itself after it goes through the cooler. I want to see if the factory oil cooler is sufficient to keep the oil cool in high load situations. I know the pan temps of the oil will go up in a high load situation, but I want to see if the stock cooler can cool it back down. Also, I was contemplating putting an external cooler on the truck, but I wanted to see what kind of post cooler temps I saw before and after. I figure if the stock cooler can keep the oil temp after the cooler at or below engine coolant temps, an external cooler won't really benefit me any.
Did I put cool and cooler in there enough?
What would you guys recommend for oil then? What is the best for our trucks, synthetic 15-40? None synthetic?
I hate the "hp" ratings on injectors and think that it is a lowsy Cummins way of rating them. With EFI Live we can tune to get "90 hp" injectors to run like stock or add 90hp without changing injectors. For tuning it would be much better to know how much more than stock they actually flow. But mine are "90hp" injectors from Dynomite. I ran no smoke down the track and didn't have any more fuel to offer from a single stock LBZ CP3. I'll be stepping up to 100% over injectors and dual CP3s with the built motor to keep PW and timing down while getting a whole lot more fuel. We'll see how it turns out.
Oil choice depends on what you use your truck for and what your clearances are on the bearings (if you have a built motor). Synthetics don't break down as much from heat as conventional oils and are good for DD, towing, and work trucks. Conventional oil holds up better under extreme pressures and is better for racing and sled pulling. With stock clearances 15-40 is good, with looser clearances in my built motor I'm going with 20-50 racing oil and changing it often. This is all my opinion but is based off research and talking to a few guys that have experimented with and analized different oils in their built and stock motors, mostly Ed Wayne.